In some network deployments, when a wireless client device roams from a current access point (AP) on a current virtual local area network (VLAN) to a new AP on a new VLAN, the wireless client device may fail to obtain a new dynamic host configuration protocol (DHCP) address on the new VLAN due to temporary network issues. As a result, the wireless client device will keep using the wrong Internet Protocol (IP) address that was previously assigned to the wireless client device on the old VLAN.
Wireless client devices often encounter DHCP issues intermittently causing failure to obtain an IP address corresponding to the new VLAN. If a client device tries to renew the IP address at a later time, the client might obtain a valid IP address. There may be a few reasons for the client device's initial failure to obtain a valid DHCP IP address. First, a temporary glitch may have occurred in the network causing a packet loss. For example, in a classroom when all students come for a class and their client devices associate with the network during the same period of time, a few of the client devices might encounter packet losses due to temporary network congestion. Those few client devices may fall back to use automatic IP addresses. Second, a temporary DHCP server failure may have occurred. Third, the DHCP lease may be temporarily unavailable.
Some client devices have mechanisms to retransmit network requests for DHCP IP address assignment in the event of a failure. For example, a Windows® client device will typically retransmit DHCP requests for three times. Specifically, the client device may send the first retry message after 4 seconds, the next retry message after 8 seconds, and the last retry message after 16 seconds. This mechanism leads to roughly 28 seconds before falling to a self-assigned automatic IP address. This process can be repeated after 30 seconds and/or every 6 minutes or so thereafter. Nevertheless, there is no existing mechanism that allows the client device to re-initiate the DHCP IP address requesting process faster upon an initial failure to obtain a valid DHCP IP address by the client device.
Therefore, client devices may benefit from an intervening mechanism to help them receive valid DHCP IP addresses after they roam to new VLANs in cases of an initial failed attempt. This will improve overall network customer experience.